1. Field of the Invention
The invention relates to piston and cylinder structures and the method of operation thereof, and refers more particularly to nitrogen cylinder structure including a hollowed out cylinder, a piston, and a hollowed out piston rod wherein there is provided a radial opening in the hollow piston rod adjacent the piston for evacuation of the space defined by the cylinder, piston, piston rod and sealing means between the cylinder and piston rod into the cylinder without contamination of the piston and cylinder structure to allow rapid, substantially trouble-free operation thereof, and the method of operation of the structure including the step of evacuating the space through the radial opening.
2. Description of the Prior Art
In the past, in piston and cylinder structures of the type wherein a hollowed out cylinder receives a piston for axial reciprocation therein having a piston rod secured thereto which extends out of one end of the cylinder and a seal is provided between the one end of the cylinder and the piston rod, the space defined between the cylinder, piston, piston rod and seal has been vented to ambient pressures generally through or around the seal between the cylinder and the piston rod or radially through the cylinder.
Such venting of this space is necessary to allow rapid reciprocation of the piston within the cylinder, since gases trapped in this area could restrict the movement of the piston and piston rod within the cylinder. Such venting has in the past lead to contamination of the piston and cylinder structure, causing rapid deterioration and inefficient operation of piston and cylinder structures.
Attempts to prevent contamination of such piston and cylinder structures in the past have taken the form of flexible accordion-type boots secured to the piston and positioned over at least a portion of the piston rod extending out of the cylinder. Also, annular collar-type structures for evacuating the area between the cylinder, piston, piston rod and seal through radial openings in the cylinder have sometimes been provided in the past connected to exhaust conduits or the like. Such structures are expensive in themselves to produce, must themselves be sealed, and are subject to damage and wear and are therefore undesirable.